The present inventive concept herein relates to energy harvesting power supply devices, and more particularly, to a piezoelectric energy harvesting array including a plurality of piezoelectric energy harvesting devices and a method of manufacturing the same.
Recently, because of the development of electrical communication technology, various kinds of electronic devices are being appeared. For example, as an electronic device such as portable electronic equipments realizes a user oriented ubiquitous computing, the demand for the portable electronic equipment is explosively being increased. Portable electronic equipments may include a portable power supply such as a battery. Since a battery technology is one-short thing or needs a periodic charge, it has limitation. In an electronic device, the need of energy harvesting has come to the fore.
A kinetic energy harvesting means a technology that can convert mechanical energy being abandoned such as the vibration of train, the vibration of vacuum pump, the vibration of machines and motors, the vibration of vehicle engine, and the vibration of human action into electrical energy. A piezoelectric energy harvesting (PEH) device is a kind of transducer. If a resonant frequency of piezoelectric energy harvesting device matches a frequency of neighboring vibration, displacement amplification is generated and thereby the highest electrical energy is generated at the resonant frequency.
A voltage being generated from the kinetic energy harvesting device is output in the form of alternating current (AC). AC voltage can be converted into a direct current (DC) to be used. DC voltage charges a super capacitor or battery and is used to drive an integrated circuit (IC). However, since electrical energy obtained from vibration being generated from the surrounding environment is very small, it is not sufficient as electric power for driving an integrated circuit. Thus, a method of optimizing a size or shape of energy harvesting device or a method of increasing an output using a multilayer structure has been studied.
Since a piezoelectric ceramic device has a brittle characteristic, it is weak to the impact and has a limit of increasing its size. In case of using a multilayer structure, since a manufacturing process is not established, it is not suited to use the multilayer structure in the manufacture of the PEH device. As another method of increasing an output of the piezoelectric energy harvesting device, there is a method of using single crystal having high coupling efficiency and a great piezoelectric constant. In this case, it is very difficult to make the single crystal into a multilayer structure.
As a method to solve the above problem, method using a piezoelectric energy harvesting array may be suggested. To match a resonant frequency of piezoelectric energy harvesting (PEH) device to a neighboring frequency (e.g., 1-120 Hz), a method of using tip mass of end of cantilever after optimizing a shape or size of the piezoelectric energy harvesting (PEH) device is frequently used.